In U.S. Pat. No. 4,292,890 a railway hopper car is disclosed in which the car body is formed by passing "E" type glass filaments through a liquid polyester resin (isophthalic acid and propylene glycol) containing styrene monomer for unsaturation to form flat bands which are wound about a mandrel in a helical winding pattern at an angle of .+-.30.degree. to the longitudinal axis.
However, in this construction the car body is subjected directly to the coupler loads applied to the coupler and which are transferred into the center sill.
In application Ser. No. 326,797 filed Dec. 3, 1981 now abandoned assigned to the same assignee as the present application, a filament wound vessel is disclosed in which at least one layer of resin impregnated glass fiber rovings is formed into bands, and hoop wound upon a rotating mandrel in a direction approximatley 90.degree. to the longitudinal axis of the mandrel. The rovings are thus orientated at approximately 90.degree. to the vessel axis. Next, at least one layer of weft unidirectional fabric comprising strands of glass fibers woven with a suitable thread in the warp direction into a relatively wide band, is hoop wound upon the first hoop wound roving layer and is applied with a resin binder. This results in the woven glass fibers being orientated along the longitudinal axis of the vessel at approximately 0.degree. Next, at least one band of resin coated rovings is helically wound at an angle of from about +40.degree. to about +60.degree., or -40.degree. to about -60.degree. to the longitudinal axis of the vessel (counterclockwise rotation being positive). Preferably, at least one additional band of resin coated rovings is helically wound in a direction opposite to the first helically wound band. Preferably, at least one layer of weft woven fabric, woven with a suitable thread in a warp direction is hoop wound with the glass strands extending along the longitudinal axis of the vessel upon the helically wound bands of rovings. Preferably at least one additional band of resin coated rovings are hoop wound in a direction approximately 90.degree. to the longitudinal axis of the vessel.
As is described in greater detail in said application Ser. No. 326,797, this construction results in a filament wound vessel having quasi-isotropic properties of a magnitude sufficient to carry lading loads encountered in railway hopper car applications.
However, even with this improved filament wound construction, it is not believed the fiberglass body is sufficiently strong and resistant to buckling to directly react coupler loads such as those resulting from impacts in switching yards and squeeze loads encountered on inclines over an extended period of car life.